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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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package org.apache.doris.nereids.trees.expressions.functions.agg;

import org.apache.doris.catalog.FunctionSignature;
import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.AlwaysNullable;
import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
import org.apache.doris.nereids.trees.expressions.shape.BinaryExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.DataType;
import org.apache.doris.nereids.types.DoubleType;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import java.util.List;

/**
 * AggregateFunction 'regr_slope'.
 */
public class RegrSlope extends AggregateFunction
        implements BinaryExpression, ExplicitlyCastableSignature, AlwaysNullable {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(DoubleType.INSTANCE).args(DoubleType.INSTANCE, DoubleType.INSTANCE)
    );

    /**
     * Constructor with 2 arguments.
     */
    public RegrSlope(Expression arg1, Expression arg2) {
        this(false, arg1, arg2);
    }

    /**
     * Constructor with distinct flag and 2 arguments.
     */
    public RegrSlope(boolean distinct, Expression arg1, Expression arg2) {
        super("regr_slope", distinct, arg1, arg2);
    }

    /** constructor for withChildren and reuse signature */
    private RegrSlope(AggregateFunctionParams functionParams) {
        super(functionParams);
    }

    @Override
    public void checkLegalityBeforeTypeCoercion() throws AnalysisException {
        DataType arg0Type = left().getDataType();
        DataType arg1Type = right().getDataType();
        if ((!arg0Type.isNumericType() && !arg0Type.isNullType())
                || arg0Type.isOnlyMetricType()) {
            throw new AnalysisException("regr_slope requires numeric for first parameter: " + toSql());
        } else if ((!arg1Type.isNumericType() && !arg1Type.isNullType())
                || arg1Type.isOnlyMetricType()) {
            throw new AnalysisException("regr_slope requires numeric for second parameter: " + toSql());
        }
    }

    @Override
    public RegrSlope withDistinctAndChildren(boolean distinct, List<Expression> children) {
        Preconditions.checkArgument(children.size() == 2);
        return new RegrSlope(getFunctionParams(distinct, children));
    }

    @Override
    public <R, C> R accept(ExpressionVisitor<R, C> visitor, C context) {
        return visitor.visitRegrSlope(this, context);
    }

    @Override
    public List<FunctionSignature> getSignatures() {
        return SIGNATURES;
    }
}
